a broad flat crater formed by a phreatomagmatic eruption

A broad, circular, low-rimmed, well-bedded accumulation of fine fragments, often 1km in diameter, around a crater. The crater of a tuff ring is wider than the one of a cinder cone.

A wide, low-rimmed, well-bedded accumulation of hyalo-clastic debris built around a volcanic vent located in a lake, coastal zone, marsh, or area of abundant ground water.

A prominent rim of consolidated ash and shattered rock encircling an explosion crater.

A wide low ring of pyroclastic material, surrounding a volcanic vent.